1. Field of the Invention
Embodiments of the invention relate to a feedthrough for a battery having a first terminal element and a second terminal element, which are at different electric potentials. Furthermore, embodiments of the invention relate to a method for manufacturing such a feedthrough and a battery having such a feedthrough.
2. Description of the Related Art
Glass-metal feedthroughs or ceramic feedthroughs are used in hermetically sealed batteries, such as those used in medical implants, ensuring an airtight electrically insulated feedthrough of a battery pole through the metallic housing. Such a feedthrough has a first terminal element in the form of a pin and a second terminal element in the form of a flange element, the two being at different electric potentials (positive pole, negative pole). Because of the slight distance between the metallic pin and the metallic flange element, even small amounts of electrically conductive material in the inner area of the feedthrough are sufficient to create a short circuit of the battery.
Such conductive materials, which create a short circuit, may be formed by dissolving the electrode materials in the electrolyte inside the battery due to the potential differences prevailing there. In the case of lithium batteries, for example, lithium may under certain conditions go into solution in the form of lithium cations. These lithium cations may be deposited in the form of elemental lithium on battery components having an anodic potential. With known batteries, to prevent short circuits in batteries due to such lithium deposits, critical components inside the battery are insulated. For example, an electrically insulating layer prevents electrons from being transferred to the ions of the electrolyte. This prevents deposits. Furthermore, deposition of metal is prevented by suppressing the wetting of the electrolyte by electrically conductive components.
In traditional batteries, glass-metal feedthroughs or ceramic feedthroughs are sealed on the inside of the battery to avoid the problems discussed above. The seal is usually provided by casting them in a polymer resin or by using a polymer plug, which is pushed onto the pin of the feedthrough. However, this procedure is very difficult to implement in the case of very small feedthroughs. Furthermore, with a small distance between the flange element and the pin, only casting materials having a very low viscosity are suitable, so the choice of casting materials is limited. This choice is additionally limited by the fact that these materials must not contain any constituents that are soluble in the electrolyte to prevent the electrolyte from damaging the casting material. The technical implementation of casting is also made difficult by the fact that the casting must be accomplished without forming pores or cavities. When using polymer plugs, there is the problem that they are usually very difficult to seal completely with respect to the pin and flange element.